1. Field of Invention
The present invention relates to an earphone plug, and more particularly to an earphone plug that is applicable to both system specifications of Open Mobile Terminal Platform (OMTP) and American Telephone and Telegraph (AT&T) by using a mechanical member to alternately switch signal interfaces of the plug.
2. Related Art
Currently an earphone is one of the indispensable parts for portable electronic products (such as, a mobile phone, a MP3 player, and a PDA). The earphone includes an earphone plug adapted to receive electronic signals, and a loudspeaker adapted to convert the electronic signals into acoustic signals. In recent years, with the rapid popularization of the mobile phone, if a user intends to use the hand-free handset function of the mobile phone, a microphone is required to add to the earphone, so as to achieve the purposes of safety and convenience in communication. Currently, the most common earphone plugs may be divided into a three-electrode mode and a four-electrode mode. The three-electrode mode is mainly used in a monophonic earphone and the four-electrode mode is applicable to a stereophonic earphone. Each electrode on the terminal of the earphone is a signal interface, which can interactively transmit electronic signals with an electronic product through the earphone jack connected with the electronic product.
FIG. 1 is a schematic view of the appearance of a conventional earphone plug. Referring to FIG. 1, the earphone plug is a currently common four-electrode earphone plug 10, and includes four signal interfaces, A1, A2, A3 and A4, which are respectively adapted to transmit left channel signals, right channel signals, microphone signals, and grounding signals. The definition of the interface is in conformity with the specification of an OMTP system, in which the OMTP is an open mobile terminal platform established by several major mobile network manufacturers worldwide (Vodafone, Orange, T-Mobile, mmO2, Telefonica, “Telecom Italia Mobile”, NTT) and is intended to put forward suggestions as reference for the design of a mobile phone so as to exert an influence on major mobile phone suppliers such as Nokia, Samsung Electronics, Motorola, and Sony Ericsson.
However, except for the above OMTP system, the signal interfaces A1, A2, A3, A4 of the earphone plug currently still can be configured in another manner, that is, the signal interface A1 transmits the left channel signals; the signal interface A2 transmits the right channel signals; the signal interface A3 transmits the grounding signals, and the signal interface A4 transmits the microphone signals. The configuration manner belongs to an AT&T system.
The above two system configurations are still prevalent in the earphone jacks and earphone plugs of many mobile phones. Thus, if a consumer inserts an earphone plug of the OMTP system into an earphone jack of the AT&T system, some sounds are eliminated, that is, the function cannot be fully performed. Thus, for the user, the safest is to use the accompanying earphone provided by the mobile phone manufacturer. However, in fact, the users always hope that their earphones can be applicable to different mobile phones; in other words, the earphones can be applicable to different system specifications. That is, no matter what type of earphone jack is encountered, the earphone plug can insert into without degrading functional performances, such as music transmission and voice transmission functions.
Thus, in order to meet the requirement of the user that a single part should be applicable to multiple products, it is necessary to improve the conventional design of the earphone plug.